CN111111459B - Polyimide/surface modified metal organic framework mixed matrix membrane and preparation method and application thereof - Google Patents

Polyimide/surface modified metal organic framework mixed matrix membrane and preparation method and application thereof Download PDF

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CN111111459B
CN111111459B CN201911348858.6A CN201911348858A CN111111459B CN 111111459 B CN111111459 B CN 111111459B CN 201911348858 A CN201911348858 A CN 201911348858A CN 111111459 B CN111111459 B CN 111111459B
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伊春海
吴东云
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Xian Jiaotong University
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D67/0002—Organic membrane manufacture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
    • B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
    • B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
    • B01D71/64—Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
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    • C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
    • C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
    • C10L3/10—Working-up natural gas or synthetic natural gas
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    • C10L3/102—Removal of contaminants of acid contaminants
    • C10L3/104—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
    • C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
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    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

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Abstract

The invention discloses a polyimide/surface modified metal organic framework mixed matrix membrane and a preparation method and application thereof, wherein the preparation method comprises the following steps: the aggregation of MOF particles can be effectively prevented by adopting dopamine surface modification, and the particle size is reduced; meanwhile, the compatibility between the MOF material and the polyimide polymer matrix is increased, and the occurrence of non-selective gaps at the polymer/MOF phase interface is reduced; CO of the polyimide/surface modified MOF mixed matrix membrane of the invention2/N2Mixed gas and CO2/CH4The result of the permeation separation performance of the mixed gas shows that the surface modified MOF doping can improve the CO of the membrane material at the same time2Permeability coefficient and CO2The selectivity of inert gas and the separation performance of the mixed gas exceed the upper limit of Robeson in 2008, which shows that the CO of the membrane can be effectively strengthened by preparing the polyimide/surface modified MOF mixed matrix membrane2Separation performance, applicable to CO in flue gas2The field of trapping and natural gas purification.

Description

Polyimide/surface modified metal organic framework mixed matrix membrane and preparation method and application thereof
Technical Field
The invention belongs to the technical field of gas membrane separation, and particularly relates to a polyimide/surface modified metal organic framework mixed matrix membrane and a preparation method and application thereof.
Background
CO2The separation and the trapping have wide application prospects in the aspects of carbon emission reduction, natural gas purification and the like, and have important significance for solving the energy and environmental problems restricting the human survival and sustainable development. Compared with traditional separation technologies such as rectification, absorption and the like, the gas membrane separation technology is widely concerned by virtue of the advantages of high efficiency, energy conservation, environmental friendliness and the like.
At present, the insufficient permselectivity of membrane materials is still one of the important factors limiting the large-scale industrial application of gas membrane separation, and the development of membranes with both high permeability and high selectivity is urgent.
In order to improve the gas separation performance of polymer membranes, researchers have proposed a number of methods; among them, the method of preparing a mixed matrix membrane by adding a porous additive to a polymer matrix is one of the most potential methods, and is expected to perfectly combine the advantages of two materials, so that the prepared mixed matrix membrane has both excellent mechanical properties and strong processability, and excellent gas separation properties. Although the mixed matrix membranes reported to date have good gas separation performance, large-scale industrial applications still face many challenges. One of the important challenges is the choice of additives that need to have specific particle size, pore size and surface functional groups and that have affinity for the gas to be separated; another important challenge is the interfacial compatibility of the additive with the polymer matrix, and if non-selective voids occur at the interface of the additive with the polymer phase, all gas molecules will readily pass through the voids and not be separated efficiently.
For porous additives, MOFs are favored by their mild preparation conditions, high specific surface area, and large pore volume. In order to improve the interfacial compatibility of MOFs with polymers, modifying the MOF surface is an effective method to improve the interfacial compatibility of additives with polymer matrices.
In view of the above, there is a need for a novel polyimide/surface modified metal organic framework mixed matrix film and a method for preparing the same.
Disclosure of Invention
The invention aims to provide a polyimide/surface modified metal organic framework mixed matrix membrane, a preparation method and application thereof, and aims to solve the compatibility problem of the existing mixed matrix membrane. The polyimide/surface modified metal organic framework mixed matrix membrane can be used for CO2And (5) separating.
In order to achieve the purpose, the invention adopts the following technical scheme:
the preparation method of the polyimide/surface modified metal organic framework mixed matrix membrane comprises the following steps:
step 1, modifying the MOF surface by dopamine to obtain surface modified MOF;
step 2, adding the surface modified MOF into an organic solvent X, and uniformly dispersing; adding a polyimide film material, performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF nano particles in a polymer solution; and preparing the polyimide/surface modified metal organic framework mixed matrix membrane with different surface modified MOF contents by solution casting and drying.
The invention has the further improvement that the step 1 specifically comprises the following steps:
step 1.1, adding MOF into a buffer solution, performing ultrasonic and then magnetic stirring, and dispersing uniformly to obtain a suspension;
step 1.2, adding dopamine into the suspension, and performing ultrasonic and magnetic stirring;
and step 1.3, centrifuging, washing with deionized water to be neutral, and drying to obtain the surface modified MOF.
The invention has the further improvement that in the step 1.1, the pH value range of the buffer solution is 7.5-9.0; the concentration of the MOF in the buffer solution is 0.4-0.6 mg/mL; the ultrasonic dispersion time is 30-90 min, and the magnetic stirring time is 12-36 h;
in step 1.2, the mass ratio of MOF to dopamine is 1: (1-3); the ultrasonic dispersion time is 15-45 min, and the magnetic stirring time is 3-18 h.
In a further improvement of the invention, in step 1, the MOF is one or more of AlFu MOF, ZIF-8, MIL-53(Al), MOF-5 and UiO-66.
In a further development of the invention, in step 2, the organic solvent X is N, N-dimethylformamide, N-dimethylacetamide or N-methylpyrrolidone.
The invention further improves the method that in the step 2, the mass ratio of the polyimide to the surface modified MOF is 1: (0.010-0.450).
The invention further improves the method that in the step 2, the mass ratio of the polyimide to the surface modified MOF is 1: (0.170-0.185).
The polyimide/surface modified metal organic framework mixed matrix membrane prepared by the preparation method provided by the invention has the thickness of 80-190 microns.
Application of polyimide/surface modified metal organic framework mixed matrix membrane prepared by preparation method disclosed by the invention to CO2Separation of inert gas.
Application of polyimide/surface modified metal organic framework mixed matrix membrane prepared by preparation method disclosed by the invention in CO (carbon monoxide) in flue gas2Capture and purification of natural gas
Compared with the prior art, the invention has the following beneficial effects:
the invention passes dopaThe amine modifies the surface of the MOF nanoparticles, which can significantly improve the interfacial compatibility between the polyimide matrix and the MOF nanoparticles. The polyimide/surface modified MOF mixed matrix membrane prepared by the invention is used for CO2/N2Mixed gas and CO2/CH4The separation of the mixed gas and the CO of the polyimide film are improved2Permeability coefficient and CO2Selectivity to inert gas.
The preparation process is simple and controllable, the conditions are mild, the technical problem of interface compatibility of the porous additive and the polymer matrix in the mixed matrix membrane can be effectively solved, and an effective method is provided for preparing the defect-free mixed matrix membrane with excellent performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below; it is obvious that the drawings in the following description are some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
FIG. 1 is a transmission electron micrograph of AlFu MOF before and after surface modification prepared in example 1 of the present invention; in fig. 1, (a) is a pre-surface-modified AlFu MOF, and in fig. 1, (b) is a post-surface-modified AlFu MOF;
FIG. 2 is a scanning electron micrograph of a cross section of a mixed matrix membrane prepared using surface modified AlFu MOF according to example 1 of the present invention;
FIG. 3 is a scanning electron micrograph of a cross section of a mixed matrix membrane prepared using surface modified AlFu MOF according to example 2 of the present invention;
FIG. 4 is a scanning electron micrograph of a cross-section of a mixed matrix membrane made using surface-modified AlFu MOF according to example 3 of the present invention;
FIG. 5 is a scanning electron micrograph of a cross-section of a mixed matrix membrane made using surface modified AlFu MOF according to example 4 of the present invention;
FIG. 6 is a scanning electron micrograph of a cross section of a pure polyimide film obtained in comparative example 1;
FIG. 7 is a scanning electron micrograph of a cross-section of a mixed matrix membrane prepared in comparative example 2 using AlFu MOF without surface modification.
Detailed Description
In order to make the purpose, technical effect and technical solution of the embodiments of the present invention clearer, the following clearly and completely describes the technical solution of the embodiments of the present invention with reference to the drawings in the embodiments of the present invention; it is to be understood that the described embodiments are only some of the embodiments of the present invention. Other embodiments, which can be derived by one of ordinary skill in the art from the disclosed embodiments without inventive faculty, are intended to be within the scope of the invention.
The preparation method of the polyimide/surface modified metal organic framework mixed matrix membrane comprises the following steps:
(1) in order to make the MOF more compatible with the polymer matrix interface, the MOF surface was modified with dopamine.
The method specifically comprises the following steps: adding MOF nano particles into a buffer solution with the pH value of 7.5-9.0, wherein the concentration of MOF in the buffer solution is 0.4-0.6 mg/mL, performing ultrasonic treatment for 30-90 min, and performing magnetic stirring for 12-36 h to uniformly disperse the MOF nano particles to obtain a suspension; then adding dopamine into the suspension, carrying out ultrasonic treatment for 15-45 min, and carrying out magnetic stirring for 3-18 h; centrifuging, washing with deionized water to neutrality, and vacuum drying at 40-80 deg.c for 24 hr.
(2) Adding the surface modified MOF into an organic solvent X, and performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF; adding a polyimide film material, continuing to perform ultrasonic and magnetic stirring to uniformly disperse the MOF nano particles in the polymer solution; and preparing mixed matrix membranes with different surface modified MOF contents by solution casting and drying.
Preferably, the mass ratio of the MOF to the dopamine in step (1) is 1: (1-3).
Preferably, the MOF in the step (1) comprises one or a mixture of several of AlFu MOF, ZIF-8, MIL-53(Al), MOF-5 and UiO-66.
Preferably, the organic solvent X in step (2) is N, N-dimethylformamide, N-dimethylacetamide or N-methylpyrrolidone.
Preferably, the mass ratio of the polyimide to the surface modified MOF in the step (2) is 1: 0.010-1: 0.450.
Preferably, the mass ratio of the polyimide to the surface modified MOF in the step (2) is 1: 0.170-1: 0.185.
Preferably, the thickness of the mixed matrix membrane in the step (2) is 80-190 μm.
Preferably, the mixed matrix membrane in step (2) is suitable for CO2Separation of inert gas.
Preferably, the mixed matrix membrane in step (2) is suitable for CO in flue gas2Capture of natural gas and purification of natural gas.
According to the embodiment of the invention, the surface of the MOF nano particles is modified by dopamine, so that the interfacial compatibility between the polyimide matrix and the MOF nano particles can be obviously improved. The polyimide/surface modified MOF mixed matrix membrane prepared by the invention is used for CO2/N2Mixed gas and CO2/CH4The separation of the mixed gas and the CO of the polyimide film are improved2Permeability coefficient and CO2Selectivity to inert gas. The preparation process of the embodiment of the invention is simple and controllable, the condition is mild, and the technical problem of interface compatibility between the porous additive and the polymer matrix in the mixed matrix membrane can be effectively solved, so that an effective method is provided for preparing the defect-free mixed matrix membrane with excellent performance.
Example 1
The polyimide/surface modified MOF mixed matrix membrane prepared by the embodiment of the invention takes self-made polyimide as a polymer matrix, and surface modified AlFu MOF is added into the polymer matrix, wherein the mass ratio of the polyimide to the AlFu MOF is 1:0.020, and the preparation process of the mixed matrix membrane is as follows:
(1) preparation of polyimide polymer matrix:
under the protection of nitrogen, 0.64mmol of self-made diaminodibenzo-18-crown-6 and 1.92mmol of commercial 2, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane are added into 9.2mL of N, N-dimethylacetamide, and are magnetically stirred to be completely dissolved to obtain a diamine solution; according to the molar ratio of the aromatic diamine to the aromatic dianhydride of 1: 1, directly adding 2.56mmol of 4, 4' -hexafluoroisopropyl phthalic anhydride solid into a diamine solution, and stirring for 24 hours at room temperature to perform solution polycondensation to obtain a polyamic acid solution. According to the molar ratio of the aromatic diamine monomer to the acetic anhydride of 1: 9, the molar ratio of acetic anhydride to triethylamine is 2:1, adding a mixed solution of acetic anhydride and triethylamine, and continuously stirring for 24 hours at room temperature to obtain a polyimide solution. Slowly pouring the high-viscosity polyimide solution into ethanol to separate out a fibrous polyimide film material, and washing the fibrous polyimide film material for three times by using ethanol; vacuum drying at 100 deg.C for 12 hr, and vacuum drying at 200 deg.C for 24 hr. Thus obtaining the polyimide polymer film material.
(2) Method for dopamine surface modification of AlFu MOF:
adding 50mg AlFu MOF into 100mL Tris buffer solution with pH of 8.5, performing ultrasonic treatment for 60min, and stirring for 24h to uniformly disperse the AlFu MOF; then 100mg of dopamine is added into the suspension, ultrasonic treatment is carried out for 30min, and stirring is carried out for 12 h; centrifuging, washing with deionized water for multiple times until the solution is neutral, and vacuum drying at 60 ℃ for 24h to obtain gray AlFu @ PD MOF nanoparticles.
FIG. 1 is a transmission electron micrograph of the prepared AlFu MOFs before and after surface modification.
(3) Preparation of mixed matrix membrane:
adding a certain amount of surface modified AlFuMOF into N, N-dimethylacetamide, performing ultrasonic and magnetic stirring to uniformly disperse the surface modified AlFuMOF, adding a polyimide film material, performing ultrasonic treatment for 1h, and performing magnetic stirring for 24h to uniformly disperse AlFuMOF nanoparticles in a polymer solution to obtain a casting solution with the mass fraction of 10%; and preparing a membrane by a solution casting method, drying at 70 ℃ for 12h, and then drying at 120 ℃ for 24h in vacuum to obtain the polyimide/surface modified MOF mixed matrix membrane.
FIG. 2 is a scanning electron micrograph of a cross section of a mixed matrix membrane made using surface modified AlFu MOF.
Use of polyimide/surface modified MOF mixed matrix membrane for CO at 35 deg.C and 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient of 163barrer, CO2/N2The selectivity is 73; simultaneously using the mixed matrix membrane for CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 155barrer, CO2/N2The selectivity was 80.
Example 2
A polyimide/surface modified MOF mixed matrix membrane was prepared. The mixed matrix membrane takes self-made polyimide as a polymer matrix, and surface-modified AlFu MOF is added into the polymer matrix, wherein the mass ratio of the polyimide to the AlFu MOF is 1: 0.053.
FIG. 3 is a scanning electron micrograph of a cross section of a mixed matrix membrane made using surface modified AlFu MOF.
Use of polyimide/surface modified MOF mixed matrix membrane for CO at 35 deg.C and 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient of 171barrer, CO2/N2The selectivity is 81; simultaneously using the mixed matrix membrane for CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 162barrer, CO2/N2The selectivity was 80.
Example 3
A polyimide/surface modified MOF mixed matrix membrane was prepared. The mixed matrix membrane takes self-made polyimide as a polymer matrix, and surface-modified AlFu MOF is added into the polymer matrix, wherein the mass ratio of the polyimide to the AlFu MOF is 1: 0.176.
FIG. 4 is a scanning electron micrograph of a cross section of a mixed matrix membrane made using surface modified AlFu MOF.
Use of polyimide/surface modified MOF mixed matrix membrane for CO at 35 deg.C and 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient of 237barrer, CO2/N2The selectivity is 89; simultaneously using the mixed matrix membrane for CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 199barrer, CO2/N2The selectivity was 83.
Example 4
A polyimide/surface modified MOF mixed matrix membrane was prepared. The mixed matrix membrane takes self-made polyimide as a polymer matrix, and surface-modified AlFu MOF is added into the polymer matrix, wherein the mass ratio of the polyimide to the AlFu MOF is 1: 0.428. FIG. 5 is a scanning electron micrograph of a cross section of a mixed matrix membrane made using surface modified AlFu MOF.
Use of polyimide/surface modified MOF mixed matrix membrane for CO at 35 deg.C and 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient 271barrer, CO2/N2The selectivity is 80; simultaneously using the mixed matrix membrane for CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 227barrer, CO2/N2The selectivity was 77.
Comparative example 1
Preparing a pure polyimide film:
(1) the polyimide film material was prepared in the same manner as in step (1) of example 1.
(2) The polyimide film material prepared above is dissolved with N, N-dimethylacetamide to prepare a casting solution with a concentration of-10 wt%, and the casting solution is dissolved at room temperature to form a uniform solution. Standing for defoaming for 12h, filtering, casting in a mold fixed on a glass plate, drying at 70 ℃ for 12h, and vacuum drying at 120 ℃ for 24 h. Thus obtaining the pure polyimide film.
FIG. 6 is a scanning electron micrograph of a cross section of the prepared pure polyimide film.
Pure polyimide film is used for CO under the conditions of 35 ℃ and 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient of 152barrer, CO2/N2The selectivity is 73; simultaneously using the pure polyimide film in CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 150barrer, CO2/N2The selectivity was 76.
Comparative example 2
A polyimide/MOF mixed matrix membrane without surface modification was prepared. The mixed matrix membrane takes self-made polyimide as a polymer matrix, and AlFu MOF which is not subjected to surface modification is added into the polymer matrix, wherein the mass ratio of the polyimide to the AlFu MOF is 1:0.176, and the preparation process of the mixed matrix membrane is as follows:
(1) the polyimide polymer matrix was prepared by the same procedure as in (1) of example 1.
(2) Preparation of mixed matrix membrane:
adding a certain amount of AlFuMOF which is not subjected to surface modification into N, N-dimethylacetamide, performing ultrasonic and magnetic stirring to uniformly disperse the AlFuMOF, adding a polyimide film material, performing ultrasonic treatment for 1h, and performing magnetic stirring for 24h to uniformly disperse AlFuMOF nanoparticles which are not subjected to surface modification into a polymer solution to obtain a casting solution with the mass fraction of 10%; and preparing a membrane by a solution casting method, drying at 70 ℃ for 12h, and then drying at 120 ℃ for 24h in vacuum to obtain the polyimide/MOF mixed matrix membrane without surface modification.
FIG. 7 is a scanning electron micrograph of a cross-section of a mixed matrix membrane made using AlFu MOF without surface modification.
polyimide/MOF mixed matrix membrane without surface modification for CO at 35 ℃ under 2.0MPa2/N2Separation of the mixture (20/80 vol%), CO thereof2Permeability coefficient of 263barrer, CO2/N2The selectivity is 72; simultaneously using the mixed matrix membrane for CO2/CH4Separation of the mixture (10/90 vol%), CO thereof2Permeability coefficient of 200barrer, CO2/N2The selectivity was 65.
TABLE 1 CO of polyimide/MOF mixed matrix membranes and pure polyimide membranes2Gas separation performance
Figure BDA0002334152800000091
As can be seen from Table 1, the following formula is given for CO2/N2Mixed gas and CO2/CH4The mixed gas is the object of separation,the gas separation performance of the polyimide/surface-modified MOF mixed matrix membrane at 35 ℃ and 2.0MPa is shown in Table 1. For polyimide/surface modified MOF mixed matrix membranes, CO increases with increasing surface modified AlFu MOF content2The permeability coefficients gradually increase and are all higher than the polyimide film of comparative example 1; CO 22/N2And CO2/CH4The selectivity showed a tendency to increase first and then decrease, and was best when the polyimide/MOF mass ratio was 1: 0.176.
Compared with comparative example 2 in which the surface-unmodified AlFu MOF is added, the mixed matrix membrane prepared by adding the surface-modified AlFu MOF has more excellent gas mixture selectivity, because the surface-modified AlFu MOF has better dispersibility and the interface compatibility of the polyimide and the surface-modified AlFu MOF is also better; in addition, the functional groups on the surface of polydopamine with CO2Has good affinity and is beneficial to CO2Thereby providing a polyimide/surface modified MOF mixed matrix membrane with higher CO2/N2And CO2/CH4And (4) selectivity.
Example 5
The preparation method of the polyimide/surface modified metal organic framework mixed matrix membrane comprises the following steps:
(1) in order to make the MOF more compatible with the polymer matrix interface, the MOF surface was modified with dopamine.
The method specifically comprises the following steps: adding MOF nano particles into a buffer solution with the pH value equal to 7.5, carrying out ultrasonic treatment for 30min when the concentration of MOF in the buffer solution is 0.4mg/mL, and carrying out magnetic stirring for 12h to uniformly disperse the MOF nano particles to obtain a suspension; then adding dopamine into the suspension, carrying out ultrasonic treatment for 15min, and carrying out magnetic stirring for 3 h; centrifuging, washing with deionized water to neutrality, and vacuum drying at 40 deg.C for 24 hr.
(2) Adding the surface modified MOF into an organic solvent X, and performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF; adding a polyimide film material, continuing to perform ultrasonic and magnetic stirring to uniformly disperse the MOF nano particles in the polymer solution; and preparing mixed matrix membranes with different surface modified MOF contents by solution casting and drying.
Wherein the mass ratio of the MOF to the dopamine in the step (1) is 1: 1.
the MOF in the step (1) comprises AlFu MOF and ZIF-8.
And (3) the organic solvent X in the step (2) is N, N-dimethylacetamide.
The mass ratio of the polyimide to the surface modified MOF in the step (2) is 1: 0.010.
Example 6
The preparation method of the polyimide/surface modified metal organic framework mixed matrix membrane comprises the following steps:
(1) in order to make the MOF more compatible with the polymer matrix interface, the MOF surface was modified with dopamine.
The method specifically comprises the following steps: adding MOF nano particles into a buffer solution with the pH value equal to 9.0, wherein the concentration of MOF in the buffer solution is 0.6mg/mL, performing ultrasonic treatment for 90min, and performing magnetic stirring for 36h to uniformly disperse the MOF nano particles to obtain a suspension; then adding dopamine into the suspension, performing ultrasonic treatment for 45min, and performing magnetic stirring for 18 h; centrifuging, washing with deionized water to neutrality, and vacuum drying at 80 deg.C for 24 hr.
(2) Adding the surface modified MOF into an organic solvent X, and performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF; adding a polyimide film material, continuing to perform ultrasonic and magnetic stirring to uniformly disperse the MOF nano particles in the polymer solution; and preparing mixed matrix membranes with different surface modified MOF contents by solution casting and drying.
Wherein the mass ratio of the MOF to the dopamine in the step (1) is 1: 3.
the MOF in the step (1) comprises ZIF-8, MIL-53(Al) and MOF-5.
And (3) the organic solvent X in the step (2) is N-methyl pyrrolidone.
The mass ratio of the polyimide to the surface modified MOF in the step (2) is 1: 0.450.
Example 7
The preparation method of the polyimide/surface modified metal organic framework mixed matrix membrane comprises the following steps:
(1) in order to make the MOF more compatible with the polymer matrix interface, the MOF surface was modified with dopamine.
The method specifically comprises the following steps: adding MOF nano particles into a buffer solution with the pH value equal to 8.0, carrying out ultrasonic treatment for 80min when the concentration of MOF in the buffer solution is 0.5mg/mL, and carrying out magnetic stirring for 24h to uniformly disperse the MOF nano particles to obtain a suspension; then adding dopamine into the suspension, carrying out ultrasonic treatment for 30min, and carrying out magnetic stirring for 15 h; centrifuging, washing with deionized water to neutrality, and vacuum drying at 70 deg.C for 24 hr.
(2) Adding the surface modified MOF into an organic solvent X, and performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF; adding a polyimide film material, continuing to perform ultrasonic and magnetic stirring to uniformly disperse the MOF nano particles in the polymer solution; and preparing mixed matrix membranes with different surface modified MOF contents by solution casting and drying.
Wherein the mass ratio of the MOF to the dopamine in the step (1) is 1: 2.
the MOF in the step (1) is AlFu MOF.
And (3) the organic solvent X in the step (2) is N, N-dimethylformamide.
The mass ratio of the polyimide to the surface modified MOF in the step (2) is 1: 0.170.
Example 8
The only difference from example 7 is that the mass ratio of polyimide to surface modified MOF in step (2) is 1: 0.185.
Example 9
The only difference from example 7 is that the mass ratio of polyimide to surface modified MOF in step (2) is 1: 0.180. In summary, the present invention discloses a polyimide/surface modified Metal Organic Framework (MOF) mixed matrix membrane, which consists of polyimide and MOF modified by surface. The aggregation of MOF particles can be effectively prevented by adopting dopamine surface modification, and the particle size is reduced; meanwhile, the compatibility between the MOF material and the polyimide polymer matrix is increased, and the occurrence of non-selective gaps at the polymer/MOF phase interface is reduced. CO of the polyimide/surface modified MOF mixed matrix membrane2/N2Mixed gas and CO2/CH4The result of the permeation separation performance of the mixed gas shows that the surface modified MOF doping can improve the CO of the membrane material at the same time2Permeability coefficient and CO2The selectivity of inert gas and the separation performance of the mixed gas exceed the upper limit of Robeson in 2008, which shows that the CO of the membrane can be effectively strengthened by preparing the polyimide/surface modified MOF mixed matrix membrane2Separation performance, applicable to CO in flue gas2The field of trapping and natural gas purification.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.

Claims (10)

1. A preparation method of a polyimide/surface modified metal organic framework mixed matrix membrane is characterized by comprising the following steps:
step 1, modifying the MOF surface by dopamine to obtain surface modified MOF;
step 2, adding the surface modified MOF into an organic solvent X, and uniformly dispersing; adding a polyimide film material, performing ultrasonic and magnetic stirring to uniformly disperse the surface modified MOF nano particles in a polymer solution; preparing polyimide/surface modified metal organic framework mixed matrix membranes with different surface modified MOF contents by solution casting and drying;
the preparation method of the polyimide polymer film material comprises the following steps:
under the protection of nitrogen, 0.64mmol of diaminodibenzo-18-crown-6 and 1.92mmol of 2, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane are used as aromatic diamine monomers and added into 9.2mL of N, N-dimethylacetamide, and the diamine solution is obtained after the diamine monomers are completely dissolved by magnetic stirring;
according to the molar ratio of the aromatic diamine to the aromatic dianhydride of 1: 1, directly adding 2.56mmol of 4, 4' -hexafluoroisopropyl phthalic anhydride solid into a diamine solution, stirring at room temperature, and carrying out solution polycondensation to obtain a polyamic acid solution;
according to the molar ratio of the aromatic diamine monomer to the acetic anhydride of 1: 9, adding a mixed solution of acetic anhydride and triethylamine into the polyamic acid solution, and continuously stirring at room temperature to obtain a polyimide solution, wherein the molar ratio of acetic anhydride to triethylamine is 2: 1;
pouring the polyimide solution into ethanol to separate out a fibrous polyimide film material; and washing and vacuum drying to obtain the final polyimide polymer film material.
2. The method for preparing the polyimide/surface-modified metal-organic framework mixed matrix membrane according to claim 1, wherein the step 1 specifically comprises the following steps:
step 1.1, adding MOF into a buffer solution, performing ultrasonic and then magnetic stirring, and dispersing uniformly to obtain a suspension;
step 1.2, adding dopamine into the suspension, and performing ultrasonic and magnetic stirring;
and step 1.3, centrifuging, washing with deionized water to be neutral, and drying to obtain the surface modified MOF.
3. The method for preparing a polyimide/surface-modified metal-organic framework mixed matrix membrane according to claim 2, wherein the surface-modified metal-organic framework mixed matrix membrane is a polyimide/surface-modified metal-organic framework mixed matrix membrane,
in the step 1.1, the pH value range of the buffer solution is 7.5-9.0; the concentration of the MOF in the buffer solution is 0.4-0.6 mg/mL; the ultrasonic dispersion time is 30-90 min, and the magnetic stirring time is 12-36 h;
in step 1.2, the mass ratio of MOF to dopamine is 1: (1-3); the ultrasonic dispersion time is 15-45 min, and the magnetic stirring time is 3-18 h.
4. The method for preparing the polyimide/surface modified metal organic framework mixed matrix membrane according to claim 1, wherein in the step 1, the MOF is one or more of AlFu MOF, ZIF-8, MIL-53(Al), MOF-5 and UiO-66.
5. The method of claim 1, wherein in step 2, the organic solvent X is N, N-dimethylformamide, N-dimethylacetamide or N-methylpyrrolidone.
6. The method for preparing the polyimide/surface-modified metal-organic framework mixed matrix membrane according to claim 1, wherein in the step 2, the mass ratio of the polyimide to the surface-modified MOF is 1: (0.010-0.450).
7. The method for preparing the polyimide/surface-modified metal-organic framework mixed matrix membrane according to claim 1, wherein in the step 2, the mass ratio of the polyimide to the surface-modified MOF is 1: (0.170-0.185).
8. A polyimide/surface-modified metal organic framework mixed matrix membrane prepared by the preparation method of any one of claims 1 to 7, wherein the thickness of the mixed matrix membrane is 80 to 190 μm.
9. Use of the polyimide/surface-modified metal-organic framework mixed matrix membrane prepared by the preparation method according to any one of claims 1 to 7 for CO2Separation of inert gas.
10. Use of the polyimide/surface-modified metal-organic framework mixed matrix membrane prepared by the preparation method according to any one of claims 1 to 7, for CO in flue gas2Capture of natural gas and purification of natural gas.
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